Electrical apparatus



April 5, 1955 J. A. SARGROVE ET AL 2,705,466

ELECTRICAL APPARATUS Filed Oct. 16, 1950 4g;- M W United States PatentELECTRICAL APPARATUS John A. Sargrove, Shepperton-on-Thames, and DenisA.

Ball, Tolworth, England, assignors to Sargrove Electronics Limited,Tolworth, England, a British company Application October 16, 1950,Serial No. 190,336

Claims priority, application Great Britain October 28, 1949 7 Claims.(Cl. 112-252 The present invention relates to electrical apparatusadapted for use in conjunction with the progressive treatment of lengthsof material.

One such progressive treatment with which the invention is concerned isthe application of a continuous thread, tape or the like to a length ofmaterial such as cloth forming part of a garment, for example by meansof a sewing machine. The rate at which such treatment can be performedon a number of ditferent lengths of material is often seriously reducedby the necessity for stopping the machine after each treatment and handcutting the portions of thread, tape or the like which extend fromeither end of a length.

One object of the present invention is to provide electrical apparatusadapted for use in conjunction with the progressive treatment of lengthsof material for automatically performing a desired operation associatedwith that treatment.

A further object is to provide electrical apparatus for use in the aboveprocess of applying thread, tape or the like to a length of material,whereby there is effected automatic cutting of the portions of thread,tape or the like which extend from each end of a length after thetreatment.

According to the present invention there is provided apparatus for usein conjunction with the progressive treatment of a length of material,comprising first means for performing a desired operation associatedwith the treatment of said material, detector means for detecting theprogress of the treatment of said material, and means controlled by saiddetector means for automatically effecting operation of said first meansbefore and after said treatment.

Thus in the application of thread, tape or the like to a length ofmaterial such as cloth, the desired operation may be the cutting of thethread, tape or the like in front of the leading edge of the length andbehind the trailing edge thereof, the means for performing thisoperation being, for example, a guillotine cutter.

For such a purpose there is provided according to the inventionapparatus adapted for use in conjunction with sewing and like machinesin which a continuous length of thread, tape, elastic or the like isapplied to a length of material, comprising cutting means for severingsaid thread, tape, elastic or the like, detector means responsive to theprogress of said material out of the work field in which said thread,tape, elastic or the like is secured relative to said material, andmeans controlled by said detector means for automatically operating saidcutting means to cut said thread or the like at a predetermined distancein front of the leading edge and behind the trailing edge of said lengthof material.

The detector means may comprise a photo-cell and associated lightprojector positioned near the outlet end of the working field, andarranged so that material leaving the working field obscures thephoto-cell. To discriminate against relatively narrow width material,such as tape, being applied to the main material two photo-cells spacedapart and connected in parallel may be used. The action of obscuring thephoto-cell or photo-cells may be arranged to cause direct operation ofthe cutting means, whilst the action of uncovering them may be arrangedto cause operation of the cutting means after the material has traveledfor a further predetermined distance. This delay may be governed bymovement of a reciprocating or rotating member forming part of themachine which may be arranged to operate contacts, for example,

2,705,466 Patented Apr. 5, 1955 at each stitching action. Thus eachaction may be arranged to add a charge to a capacitor until thepotential developed across the capacitor is sufiicient to cause atriggering action which results in operation of the cutting means.

Suitable means may be provided for disabling the automatic control andreplacing it by hand control and for preventing operation of the cuttingmeans when the material is stationary.

One embodiment of the present invention will now be described, by way ofexample, as applied to electrical apparatus for use in conjunction withsewing machines whereby the threads extending from each end of a lengthof material after treatment are automatically cut off at a predetermineddistance from the appropriate end.

The embodiment will be described with reference to the accompanyingdrawing, the single view illustrated being a combined electrical andmechanical schematic presentation which shows the cutting means, itsassociated detector means and control circuits for effecting operationof the cutting means.

The electrical apparatus in this embodiment is intended for use with aso-called Flat lock sewing machine having four needles and with fivethreads in the' top working foot and four threads in the bottom work armproducing in the working field a fiat plaited thread structure termed achain. While the sewing machine is correctly operating it forms thischain irrespective of whether there is any material to sew or not. Thusif the machine is started before the material to be sewn is inserted inthe working field a short piece of chain precedes the material, also apiece of chain follows the emerging end of the piece of sewn material.Both these ends are usually cut or trimmed off by hand during whichperiod of time the machine is inoperative.

Mounted near the outlet end of the working field is a thread-cuttingguillotine constructed so that it is capable of cutting off theprotruding threads which precede the leading edge, and follow thetrailing edge, of the material coming from the working field, thecutting taking place at a predetermined position from those edges. Theelectrical apparatus to be described is designed to controlautomatically the operation of this guillotine, and comprises detectormeans responsive to the presence or absence of material adjacent to theoutlet end of the working field and control circuits fed from thedetector means and controlling the operation of the guillotine.

Referring now to the drawings, the detector means comprises a pair ofphoto-electric cells 10 mounted adjacent to each other in the bottomwork arm of the machine, both at the same distance from the needles (notshown) but spaced apart at substantially the same distance as the widthof the thread chain. These photocells 10 co-operate with a small lightprojector 11 mounted close to the top working foot. The arrangement issuch that material emerging from the working field will prevent thelight from the projector 11 illuminating the photo-cells 10, the chaindue to its limited width not being able to obscure both photocells 10 atthe same time. The two photo-cells 10 are connected in parallel across acommon high resistance load R1, and the light intensity is arranged tobe such as to bring the standing voltage of the cells 10 beyond the bendin their output characteristic so that the output voltage issubstantially independent of Whether one or both cells 1.0 is or areilluminated; thus obscuring of a single cell by the chain will have noeffect.

The photo-cells load resistance R1 is connected in the input circuit ofa three stage direct-coupled amplifier 12 forming part of the controlcircuits. The anode circuit of the last stage contains a relay A/2,which has two moving contacts a1 and a2 each co-operating with a singlefixed contact. With at least one of the photo-cells 10 illuminated theoutput from the amplifier 12 is arranged to be suliicient to operaterelay A/Z. The control circuits include a fourth triode amplifier valveV4 (which as shown is one section of a double triode valve), the othersection of which forms the last valve in the amplifier 12. The anodecircuit of V4 includes a relay B/2, which has two moving contacts b1 andb2 each movable between two fixed contacts.

The fixed front contact co-operating with moving contact bz is commonedto the fixed back contact co-operating with the moving contact b1 andthese commoned fixed contacts are joined to the positive terminal of arectifying and smoothing circuit 13 which supplies the high tension forthe valves and is itself supplied from mains terminals 20 through aconstant voltage transformer 9. The other two fixed contacts arecommoned and joined to the negative earthed terminal of the supply. Themoving contact be is connected in series with a capacitor C2 of, forexample, one micro-farad, and a relay C/l to the moving contact hr. Theeffect of this arrangement is that a change of state of operation ofrelay B/2 causes a reversal of the polarity of the voltage appliedacross the relay C/1 and capacitor C2, so that a pulse of current passesthrough the relay C/1 energising it for a short period. Thus the relayC/l is energised for a short period at every change of state ofoperation of the relay B/2. The relay C/1 has a pair of contacts 01included in the circuit of a solenoid 14, the contacts 01 being closedon energisation of the relay C/ 1. The solenoid armature 15 is coupledmechanically to the moving blade of the thread-cutting guillotine 16.

The grid of the valve V4 is connected to earth through the movingcontact a1 when relay A/2 is not energised. The cathode of the valve V4is connected to a point of positive potential on a potentiometer formedby resistors R2, R3 and R4 which are connected across the high tensionsupply, the potential being sufficient to cut off the anode current whenthe grid is earthed. The potential can be adjusted over a limited rangeby movement of the slider of resistor R2. The grid of valve V4 is alsoconnected to earth through a capacitor C3 of relatively large capacity,for example one micro-farad, which is fed through a resistor R5 ofrelatively high resistance, for example ten megohms, from a point 17 ofhigher POSI- tive potential than that to which the cathode is connected.The potential at the point 17 is derived from a bridge rectifier 26supplied from a secondary winding of a transformer 27 whose primarywinding is connected to the mains terminals 20. A further secondarywinding of the transformer 27 provides the heater current for the valvesV1 to V4. This means that if relay A/2 is energised so that the grid ofvalve V4 is disconnected from earth the capacitor C3 will ,charge up ina predetermined time and raise the grid potentral to render valve V4conductive. The capacitor C3 is also connected through the movingcontact a2, when relay A/2 is energised, to the back contact associatedwith a moving contact d1 controlled by a relay D/1. The moving contactd1 is connected to earth through a capacitor C4 which is ofapproximately one tenth of the capacity of the capacitor C3. When therelay D/1 is unenergised the moving contact d1 rests on a front contactconnected to the point 17 of positive potential from which the capacitorC3 is charged so that the capacitor C4 is charged when relay D/l isunenergised. The relay D/l is preferably of the high speed type and hasan actuating contact 18 arranged to be operated by a cam 19 mounted on arotating component in the head of the sewing machine so that the relayD/l is pulsed every time a stitch is made by the sewing machine. Thearrangement is such that immediately after the relay A/2 is energisedthe capacitor C of large capacity is uncharged and the capacitor C4 ofsmall capacity will be connected across the large capacitor C3 once perstitch and transfer a charge to it, thus charging-up the capacitor C3more quickly than it would be charged through the resistance R5 providedthat the stitches occur fairly rapidly. With the small capacitor C4having one tenth of the capacity of that of the capacitor C3, the latterwill be fully charged after approximately ten stitches and the valve V4thereupon rendered conductive. The number of stitches required can, ofcourse, be varied by varying the ratio of the capacity of the twocapacitors C and C4. It will be seen that provided the stitches occursufficiently rapidly for the capacitor C3 to be charged from the smallcapacitor C4 rather than through the large resistor R5, the time atwhich the valve V4 becomes conductive will be dependant only upon thetime in which the predetermined number of stitches occur after theenergisation of relay A/2.

The last valve V3 in the amplifier 12 and the valve V4, which controlco-operating relays A/2 and B/2 respectively, are preferably the twoportions of a double triode valve as shown or are connected with theirfilaments in series in order to fail simultaneously. This also appliesto the first two valves V1 and V2.

The solenoid 14 is fed from an alternating current supply, connected tothe terminals 20, through an energising circuit which includes thecontacts 01, a safety switch 21 of the microswitch kind which is openwhen the sewing machine is stationary and is operated with the machineclutch through the wire 22 which raises the lever 23 when the clutch isengaged, and an isolator switch 24 by which the automatic operation canbe stopped but which keeps the valves in a stand-by condition with thecathode heaters alight. There is also an alternative solenoid operatingcircuit provided by a hand impulsing switch 25 by which the guillotine16 can be operated even when the machine is stationary.

A preferred sequence of operation will now be described. With themachine stationary and no material in it the photo-cells 10 are exposedto light. Relay A/2 is energised and the grid of the valve V4 isdisconnected from earth, so that the large capacitor C3 can be chargedslowly through the high value resistor R5 until it attains a voltage atwhich the valve V4 conducts and relay B/2 is energised. This latterresults in the relay C/l being pulsed, but the guillotine operatingsolenoid 14 is not energised as the safety switch 21 is open. If now themachine is started and material is placed in the machine, thephoto-cells 10 will remain exposed until the leading edge of the treatedmaterial emerges from the working field, when relay A/ 2 becomesunenergised. The grid of the valve V4 is thus earthed and relay B/2becomes unenergised causing relay C/1 to be pulsed. This completes theguillotine solenoid circuit to pass a large A. C. pulse through thesolenoid 14 and operate the guillotine 16 for a short period thuscutting off the thread chain protruding from the leading edge of thematerial. The guillotine 16 being further from the working field thanthe photo-cells 10 can be arranged to cut the chain in the requiredplace ahead of the leading edge. As the material proceeds through themachine the photo-cells 10 remain obscured so that relays A/2, B/2 andC/1 are unenergised. Only the relay D/1 is energised once per stitch butthe small capacitor C4 cannot transfer its charge to the large capacitorC3 as the circuit is broken by the unoperated movable contact a2. Whenthe trailing edge of the material emerges from the working field thephoto-cells 10 are again exposed to light, relay A/2 is energised andthe earth is removed from the grid of the valve V4. The small capacitorC4 now transfers its charge to the large capacitor C2 until thepredetermined number of stitches have been made when the potential ofthe large capacitor C3 is sufiicient for anode current to pass in thevalve V4 and thereby operate the relay B/2. Or to put the mattersomewhat differently, the time that valve V4 becomes conductive dependsnot upon time as such but rather upon the number of stitches which takesplace as measured by a corresponding number of revolutions of the shafton which cam 19 is mounted. The means for counting the number ofrevolutions of that shaft are the cam 19, contacts 18, relay D/1 andcapacitors C3, C4. As before this results in operation of the guillotine16 which cuts the thread chain behind the trailing edge, provided thatthe machine is still running and the safety switch 21 is thus closed.The control circuit is now in the same condition as first described sothat if the machine continues to run and if further material is fed in,the automatic thread cutting will continue as desired. It will be seenthat the arrangement by which the guillotine 16 operates on the chainsucceeding the trailing edge is such that the operation of theguillotine 16 depends only upon the number of stitches made after thetrailing edge leaves the working field and uncovers the photo-cells 10,provided that the machine is operating at a reasonable speed. The numberof stitches which cause operation can be varied by adjustment of theslider of resistor R2. A simple time delay circuit would not be suitableas it would be dependant upon a constant operating speed of the machine.This would be diflicult to guarantee, particularly as the second cut ismade at a time when the operator is instinctively tending to slow up themachine, particularly when the operators attention is directed toinserting a fresh piece of material into the machine. With a simple timedelay circuit a considerable slow-down might lead to cutting of the material itself. Moreover, such a delay circuit would have to be switchedfor operation on the trailing edge cut only. The safety switch 21prevents automatic operation of the guillotine 16 when the machine isstationary so that operation cannot occur whilst material is beinginserted into the working field from any direction, thus protecting boththe material and the'operator.

n sewing machines adapted for the insertion of tape or elastic it isadvantageous in addition to the above features to arrange a towingdevice for extracting the material from the sewing machine in a flat andorderly manner. In the absence of this the tape or elastic wouldcontract on emergence and bend and deform the material so that thephoto-cells could not correctly sense the edges of the material and theguillotine 16 would not operate correctly.

It is important to ensure the accurate positioning and alignment of theblades of the guillotine 16. The bottom blade is desirably a solidfixture though adjustable whilst the top blade should be adjustable aswell as flexible.

A desired arrangement may also contain two or more guillotine bladeseach operated separately or jointly according to desired combinations.The blades may be at different angles and combined with differentcombinations of photo-cells. Moreover instead of employing directelectrical operation the guillotine may be mechanically operated andmerely have an electrically operated release.

The indication as to whether the sewing machine is operating can also bemonitored by using the impulses from the stitch counter or a rotarycentrifugal governor type of switch instead of the clutch operatedsafety switch.

Many other modifications may be made to the detailed arrangementdescribed; thus for example it may be more convenient to use photo-cellsand a light source mounted in the same housing and provide a lightreflector on the opposite side of the path which the material takes, orthe stitch counter may take the form of a commutator.

It will be seen that by using apparatusof the kind specified whenapplying thread, tape or the like to successive lengths of material,production can be continuous as there is no requirement either during orafter the process to cut by hand the thread, tape or the like.

What we claim is:

1. In combination with a sewing machine adapted to produce a plaitedchain of thread and to sew the same onto a length of material fedthrough the machine, means for cutting said thread chain, detector meansadapted to be responsive to the passage of the trailing edge of materialfrom the stitching position of said machine, and means responsive to thestitching action of the machine and initialed by said detector means foreffecting operation of said cutting means a predetermined number ofstitching actions behind the trailing edge of the material, the meansresponsive to the stitching action of the machine comprising a firstcapacitor, a second capacitor having a relatively larger capacitancethan said first capacitor, means for charging said first capacitor,means operable by the stitching mechanism of said sewing machine fortransferring the charge on said first capac1tor to said second capacitorat each stitching action, the minimum interval between the transferenceof charge being such that said first capacitor is fully charged beforeeach transference, and means connected to said second capacitor andresponsive to the attainment thereby of a predetermined charge foreffecting cutting of said chain, said predetermined charge being amultiple of the full charge of said first capacitor, said multiple beingsubstantially equal to said predetermined number of stitching actions.

2. Apparatus according to claim 1, in which the means for transferringthe charge comprises a movable contact member connected to said firstcapacitor and movable between a contact connected to said means forcharging the first capacitor and a contact connected to said secondcapacitor.

3. In a sewing machine having means for feeding material therethroughand simultaneously sewing it, the combination comprising a cuttingdevice mounted on the machine for cutting the material after it has beensewn, and spaced light source means and co-operating photocell meanshaving a light path between them that is in the path of movement of thematerial when it is moved through the sewing machine, means responsivewhen the material fed through the machine reduces the light transmittedfrom the light source means to the photocell means for operating saidcutting device, and means responsive when the light transmitted to thephoto-cell means increases due to further feeding of the material foragain operating said cutting device after a predetermined delay, saiddelay being determined by the material feed of said machine andcorresponding to the passage of a predetermined length of materialthrough said machine.

4. Apparatus according to claim 3, in which said photo-cell meanscomprises a pair of photo-cells spaced apart, the distance between saidphoto-cells being less than the width of the material being treated.

5. Apparatus according to claim 3, in which means are provided forpreventing operation of said cutting device when said sewing machine isstationary.

6. In combination with a sewing machine adapted to continuously producea plaited chain of thread and sew the same onto a length of material fedthrough the machine, detector means for detecting the departure of thetrailing edge of the material from the stitching position of saidmachine, a moving portion on said machine actuated in accordance withthe material feed of said machine, means connected to said movingportion and controlled thereby for measuring a predetermined distancetraveled by the trailing edge of the material from the stitchingposition of said machine, said measuring means being initiated by saiddetector means, and means controlled by said measuring means for cuttingsaid thread chain.

7. The combination as defined in claim 6 wherein the moving portion ofsaid machine actuated] in accordance with the material feed thereof isconstituted by a rotary shaft, and said means controlled by said movingportion for measuring the passage of a predetermined length of thematerial from the treatment zone .includes means initiated by saiddetector means for counting the revolutions of said rotary shaft.

References Cited in the file of this patent UNITED STATES PATENTS

